The present invention generally relates to wireless communication network management, and in particular relates to a method of reducing call setup latency when transitioning an established packet data call from a dormant to an active state.
Traditionally, wireless communications networks have existed to support primarily voice services. Voice and similar continuous, point-to-point communications services (e.g., facsimile transmission) are known as circuit switched services, wherein a logical traffic channel is dedicated to the communication session (also referred to herein as a “call”). Increasingly, however, wireless communications networks are being called upon to deliver a broad range of data services, such as email, Web browsing, Instant Messaging (IM), multicasting, multimedia streaming, various Short Messaging Services (SMS), including stock tickers and weather/travel updates, transferring image and video data and the like. Both the range of such non-voice data services and their volume is expected to increase. Such data services are referred to as packet switched services, wherein a dedicated traffic channel is not permanently allocated to each call. Rather, data is packaged into logical, addressable units called packets, and transferred to and from mobile terminals, according to a packet-based network protocol, such as TCP/IP. One option in the wireless communication standard cdma2000 that supports packet data calls is Service Option 33 (SO33), as specified in TIA/EIA/IS-707-A-1.12 or later revisions.
A significant difference between packet switched services and circuit switched services such as voice, is that the packet switched services carry “bursty” data. That is, packet data connections transfer data intermittently, with often significant periods of non-activity bracketing often short periods of voluminous data transfer, depending upon the nature of the service or services being supported. For example, a user engaged in Web browsing typically clicks a link, receives a page download, and peruses the downloaded page for some time before clicking another link or otherwise causing another page to load.
To efficiently deploy limited network resources, packet data connections may be managed based on the “states” of those connections. Resources may be incrementally allocated and deallocated in staged fashion based on the particular state of a given data connection. In cdma2000 networks for example, a packet data call may assume the following states: Active, Control Hold, Idle, and Dormant.
In the active state, the network maintains a full allocation of resources, including dedicated MAC and traffic channels, such that data may be actively received from or transmitted to a user's mobile terminal. If no data is transferred between the network and the mobile terminal within a defined time window, the user's data connection may transition to a dormant state, in which network resources such as traffic channels are freed up to serve other mobile terminals. Upon transition from a dormant to an active state, the wireless communication network allocates the necessary network resources to again provide full data transfer capability to and from the mobile terminal. However, a significant amount of overhead is required in prior art systems to re-establish a packet data call to a mobile station when the call transitions from a dormant to an active state.
For packet data calls in cdma2000, Radio Link Protocol (RLP) is used to transmit and retransmit packet data between the mobile station and a network node such as a base station controller. RLP uses the RLP Sync exchange procedure to estimate the round-trip-time (RTT) between peers of the RLP. The RTT is used in the procedures to retransmit NAKs (Negative Acknowledgement Requests) between peers of the RLP. Prior to the exchange of any user data, RLP needs to perform the RLP Sync exchange procedure to determine the value of RTT. The RTT is then used to derive the RLP REXMIT_TIMER (re-transmit timer). RLP uses the REXMIT_TIMER for processing the NAK list during RLP NAK retransmissions.
An additional requirement in many prior art wireless communication systems to transition a packet data call from dormant to active is a service negotiation procedure as part of the call setup process. One example of a service negotiation procedure for a packet data call is the exchange of a Service Request Message (SRQM) and Service Response Message (SRPM)—perhaps several iterations—followed by a Service Connect Message (SCM) and a Service Connect Completion Message (SCCM) between the base station controller and mobile station. Service negotiation could also occur during a call, e.g., when adding additional service instances using the EOM, CLAM, SRQM, SRPM, SCM, SCCM or UHDM/GHDM.
Both the RLP Synch Exchange and service negotiation procedures contribute to the call setup latency. For applications such as Push To Talk, call setup latency reduction is important to improving the end-user experience. Call setup latency reduction is important to other services also, such as in the establishment of circuit switched voice and packet data services concurrently, and multiple service instances, such as for example up to six packet data service instance. The present invention may reduce call setup latency in all these cases.